Retinal branch vein occlusion is one of the most common diseases of the retinal vessels. In this retrospective study, 27 affected eyes were reviewed to determine the natural history, complications, and visual prognosis. Retinal branch vein occlusion most often involves temporal retinal veins at the arteriovenous crossing. The precise cause is unknown, but a high degree of association with systemic hypertension and diabetes mellitus is known. The clinical and fluorescein angiographic appearance of acute and chronic retinal branch vein occlusion is described and illustrated. The most common complications affecting visual acuity are macular edema and preretinal neovascularization. It is imperative that collateral channels be distinguished from neovascularization. If the patient's initial visual acuity is good, the prognosis is excellent, but if the initial acuity is poor, the visual outcome is less certain.